Emissions control of internal combustion engines has become a priority in recent years and emissions control regulations continue to set more stringent standards for the emissions produced by modern-day engines. More particularly, these regulations often target emissions contained in the exhaust produced by internal combustion engines including carbon monoxide, carbon dioxide, NOx, unburned hydrocarbons and particulate matter, which is mostly soot. As such, manufacturers of compression ignition engines and spark ignition engines alike have developed various emissions control devices. Such emissions control devices include exhaust oxidation catalysts that remove carbon monoxide, hydrocarbon, and NOx emissions and exhaust particulate filters that remove particulate matter.
In testing engines for emissions compliance, it is desirable to determine the mass of pollutant in the exhaust produced by the engine. However, accurate calculation of the pollutant mass is problematic when the time of measurement of a pollutant concentration and an exhaust flow rate are not properly synchronized.
Multiple instruments are used to measure the necessary parameters for calculating the pollutant mass including, for example, exhaust flow rate and soot concentration. The multiple instruments generate signals that are not easily synchronized in time because the signals generated by the instruments may be captured by different recorders and/or may not start out aligned in time. Furthermore, there may be a gain or loss of time between the signals when measured over a testing interval if the clock rates are slightly different. Without first synchronizing the signals that carry the exhaust flow rate and pollutant concentration data, it is not possible to accurately calculate the pollutant mass. What is needed is a system and method for synchronizing these signals in time at the beginning of the testing interval and all points occurring along the testing interval such that accurate pollutant mass values can be calculated.